Factoring M7777171

[gLauss]

Originally Posted by VBCurtis

Curves at B1=50k could still find a factor, but B1=250k will have more than 5x the chance per curve (while taking about 5x as long, so odds-per-day improve).

I know. If you take a look, I did put more total effort into B1=250k curves than B1=50k. However, I ran only a few of them. According to the report_ecm, what I did in total is equivalent to 170 curves of t25. I think it is kind of unlikely for this number to have a factor less than 30 digits because of the very large P-1 bounds, too. And t35 is way beyond what I'm willing to spend on this stupid task

[Viliam Furik]

I TFed the M20825573 to 78 bits, 79 is on the way. So far, no factor.

[gLauss]

Originally Posted by Viliam Furik

I TFed the M20825573 to 78 bits, 79 is on the way. So far, no factor.

Hihi, thanks for that! My laptop GPU is too crappy for this bitlevels. However, I assume your chances for success are quite low because of the large P-1 and the ECM curves I already ran. I won't continue on this number for now, back to boring PRP testing...

[Zhangrc]

I'd like to factor M19491001, just because the way it looks.
I did TF to 2^75 and dozens of ECM curves because I noticed that a prior P-1 has been done. So far, no factor was found.
Should I do P+1 or try P-1 with larger bounds?

[VBCurtis]

I wouldn't do another P-1 until I'd finished the B1 = 50k ECM level. I'd do a few curves at B1=250k also before repeating P-1.

If I did another P-1. I'd increase the bounds by 10x or so. You have to re-do all the work of the previous P-1, so increasing bounds just a little bit means you're mostly wasting work (and thus that there are better ways to use those cycles).

P+1 seems like a reasonable choice- again, pick big bounds- big enough that you won't be tempted to try even-bigger ones later. How big to pick depends quite a bit on how much effort you want to spend on this factoring effort- completing the B1=50k level is non-trivial, but completing the B1=250k level is a pretty serious effort. If you intend to go that far, choose bigger P+1 (and maybe P-1) bounds than would normally be reasonable.

[Viliam Furik]

Originally Posted by Zhangrc

I'd like to factor M19491001, just because the way it looks.
I did TF to 2^75 and dozens of ECM curves because I noticed that a prior P-1 has been done. So far, no factor was found.
Should I do P+1 or try P-1 with larger bounds?

I wanted to go do TF on my new RTX 3080, but it seems I need a new version of mfaktc, compiled for CUDA runtime v11.40. So I'll do it on my RTX 2080Ti. 75 to 78 bits. See you tomorrow.

[gLauss]

Originally Posted by VBCurtis

If I did another P-1. I'd increase the bounds by 10x or so. You have to re-do all the work of the previous P-1, so increasing bounds just a little bit means you're mostly wasting work (and thus that there are better ways to use those cycles).

P+1 seems like a reasonable choice- again, pick big bounds- big enough that you won't be tempted to try even-bigger ones later.

As I am stuck with "my number" and don't want to waste full t30 level, I will now run a P-1 with B1=15M and then two P+1 with B1=7.5M for 19491001. Let's see if I get lucky...

[Prime95]

Originally Posted by gLauss

As I am stuck with "my number" and don't want to waste full t30 level, I will now run a P-1 with B1=15M and then two P+1 with B1=7.5M for 19491001. Let's see if I get lucky...

Stop! Investigate v30.8. Wait for a future version before trying P+1.

[mrh]

I gave it some more P-1, but still it resists...

https://www.mersenne.ca/exponent/7777171

[VBCurtis]

Originally Posted by gLauss

As I am stuck with "my number" and don't want to waste full t30 level, I will now run a P-1 with B1=15M and then two P+1 with B1=7.5M for 19491001. Let's see if I get lucky...

Why so small? For the time you've put into trial factoring, why not put a core-week or more into P-1?

Using 30.8 with a bunch of memory (16GB or more), I imagine B1 = 50M with the big B2 from 30.8 will give you something like 7-8% chance to find a factor. Again, don't do a calculation that you'll be tempted to redo later. Do P-1 once, so big you won't ever consider repeating it.

[LaurV]

Originally Posted by VBCurtis

Again, don't do a calculation that you'll be tempted to redo later. Do P-1 once, so big you won't ever consider repeating it.

+1